DaemonBus (was EventBus): typed events for system/IPC layer.
MessageBus: channel-based pub/sub for UI/extension coordination.
Messages carry publisher (auto-stamped from extension ID),
channel (required), timestamp, and payload. Subscribe by
publisher, channel, or both — zero collision across extensions.
Extension context gains publish() and subscribe() convenience
methods that auto-stamp the extension's ID as publisher.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>